Skin care composition

ABSTRACT

The present invention relates to a method for treating spots and other symptoms of acne and related skins disorders in mammals, which comprises applying to the affected area of the skin of the mammal a non-aqueous composition comprising a dermatologically effective amount of a particulate silica, silica hydrate or precursor thereof. The invention also provides compositions for topical application to the skin which comprise particulate silica, silica hydrate or a precursor thereof in a non-aquous carrier medium.

This application is a 371 of PCT/GB97/00048 filed on Jan. 8, 1997.

The present invention relates to a method and composition, notably to amethod for the treatment of acne and a composition for topicalapplication in such a method.

BACKGROUND TO THE INVENTION

Many people suffer from acne and related skin disorders in which thesebaceous glands secrete excessive amounts of oily material and causelocalised accumulations of oils in the surface layers of the skin,giving rise to unsightly red spots or areas of skin. In extreme cases,these spots can become infected and cause damage to the skin. Forconvenience, the term acne will be used herein to denote skin disorderswhich result from secretions of sebum in the skin whose symptoms includeskin rashes and inflammations as well as spots and pimples.

There have been many attempts to provide successful treatment for acne,and many of these have been based upon anti-biotic formulations.However, these are expensive and do not provide immediate and effectivetreatment.

I have now found that fine particulate silica, notably colloidal orprecipitated silica or partial hydrates thereof, is remarkably effectivein providing rapid alleviation of the symptoms of acne and related skindisorders, that is the spots, inflammation and red areas of the skincaused by the underlying disorder.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides a method for the alleviationof the symptoms of acne and related skin disorders in mammals, whichmethod comprises applying to the affected area of the skin of the mammala non-aqueous composition comprising a dermatologically effective amountof a particulate silica, which may be an anhydrous form or a partialhydrate thereof or precursor thereof.

The invention also provides a dermatologically active composition fortopical application to the skin of a mammal suffering from acne, whichcomposition comprises a dermatologically effective amount of aparticulate silica, which may be an anhydrous form or a partial hydratethereof or precursor thereof, in an non-aqueous carrier medium.

For convenience the term silica will be used herein to denote silicaitself, that is SiO₂ ; partial hydrates of silica, for example those ofthe formula Si[SiO]₂₋₄ [OH]₁₋₂ ; those amorphous materials known asprecipitated silica, colloidal silicon dioxide and fumed silica; silicicacid; or silica gel. A particularly preferred form of silica for presentuse is that fumed silica sold by Degussa AG under the trade markAerosil.

The silica for present use may also be used in the form of a precursorthereof, for example a higher hydrate of silica which readily loseswater of hydration due to the heat generated during milling to reducethe particle size of the initial material to the desired small particlesize so as to form the desired lower hydrate in situ. The term silica istherefore used herein wherever the context permits to include othercompounds of silicon, notably the organic derivatives of silicon and thehigher hydrates of silica, which form the desired form of silica in situduring the processing of the ingredients to form the compositions of theinvention.

For convenience, the invention will be described hereinafter in terms ofthe use of fine particle size silica.

I believe that the compositions of the invention act by way of removalof fluid from the affected area of the skin causing the fluid secretionin the skin to migrate to the topically applied composition where itabsorbed or adsorbed by the silica deposited on the skin from thecompositions of the invention. That silica itself should be effective inthe treatment of acne and related disorders is highly unexpected in viewof the known inert nature of silica. I believe that, in the case of someforms of the silica, the fluid is absorbed by the silica as water ofhydration and/or combination, for example in the case of silica gel.However, in other cases, the fluid is adsorbed within the inter-particleinterstices of the deposit of silica particles on the skin due tocapillary action. This latter mechanism has never been proposed beforeto remove fluid from acne affected areas of the skin and reduces therisk that the compositions of the invention are rendered less effectivedue to absorption of water from the atmosphere as opposed to theunderlying skin. It is within the scope of the present invention to usemixtures of silica which act both by absorption of fluid as water ofhydration or combination and by adsorption of fluid by capillary action.

The silica is preferably used in a form which maximises the capillaryaction of the silica on the underlying skin to which it is to beapplied, and this is conveniently achieved by the use of a fineparticulate form, of the silica, notably that with an average primaryparticle size of less than 10 micrometers, notably less than 5micrometers. A particularly preferred form of silica for present use isfumed silica which has an average primary particle size of less than 0.1micrometer. Such fine particle size silica is available commercially andmay be used in its commercially available forms in the presentinvention.

It may be desired to treat the surface of the silica particles to renderthem more easily wet by the fluid removed from the skin. Such surfacetreatment includes at least partial coating of the silica particles witha polar material, for example a short chain alkylamine, notably mono- ordi-ethylamine, or with a surface active agent. Typical surface activeagents include anionic surfactants such as alkarylsulphonates, non-ionicsurfactants such as long chain alkane glycols or polyalkylene glycols,notably polyethylene glycols. Such surface treatments of the silicaparticles can be achieved, for example, by milling the particles andsurfactant together, for example in an air mill or a ball mill. Thepre-treatment may also reduce the tendency of the silica particles toagglomerate before they are incorporated into the compositions of theinvention. The amount of surfactant required to provide satisfactorypre-treatment of the silica particles can be readily established bysimple trial and error tests, but will typically be in the range 0.1 to5% by weight of the silica. If desired, the surfactant can be put up inpart of the alkanol, glycol or other fluid carrier to be used in thepreparation of the composition of the invention to form a slurry of thepre-treated silica for storage and transport prior to use in thepreparation of the compositions of the invention.

In use, the composition of the invention is applied to the affected areaof the skin and allowed to dry, if put up in a fluid carrier medium. Theresultant silica deposit containing the absorbed or adsorbed secretionfrom the skin can be removed from the skin as a solid. Alternatively,the deposit can remain upon the skin as an ingredient in adermatologically acceptable cosmetic composition. It is thereforepreferred to put the silica up in a carrier which readily dries upon theskin so as to minimise the formation of greasy deposits upon the skin orin the underlying epidermal layers. Preferably, the silica is put un ina non-oleaginous carrier, notably one which readily vaporises at skintemperature. The use of a volatile carrier for the silica particles alsoaids formation of fine passages or interstices in the silica deposit onthe skin formed when the carrier volatilises from the composition whichI believe assists the capillary action of the silica deposit on theskin. Preferred carriers for the silica are thus short chain aliphaticalcohols or glycols, notably those containing from 1 to 4 carbon atoms.Where the alcohol or glycol contains more than 2 carbon atoms, it ispreferred to use branched chain materials, for example iso-propylalcohol. Other carriers which may be used are dermatologicallyacceptable esters or ketones in which the alkyl moieties contain from 1to 4 carbon atoms, for example ethyl acetate or acetone, and mixtures ofthe above carriers with themselves or other dermatologically acceptableingredients. However, the use of ethanol, for example in the form ofsurgical spirit, denatured alcohol or methylated spirits, isparticularly preferred since it rapidly evaporates from the skin andaids the formation of a deposit of silica which is closely adherent tothe skin and thus aids migration of fluid from within the skin.

Mixtures of carriers with other materials may be used; for example withrheological modifiers or suspension stabilisers, for examplepolyalkylene glycols, polyalkylene ether glycols or cellulosederivatives, and acrylic acid polymers such as the acrylate polymerssold under the Registered Trade Mark Carbopol; moisturising agents, suchas urea; and diluents or emulsifying agents where the carrier is in theform of a non-aqueous emulsion, may also be used.

The compositions may thus be put up in the form of a substantiallyodourless suspension of silica particles in an alcohol carrier,typically as a thick paste, gel or slurry containing from 2 to 50%,preferably 5 to 25%, notably 7.5 to 20% by dry weight of silica.However, it will usually be desired to incorporate one or morefragrances, opacifying agents and other cosmetic ingredients into thecomposition so that it provides a cosmetic effect when applied to theskin in order to mask the residual silica particles upon the surface ofthe skin. Thus, the composition can be put up in a conventionalnon-aqueous foundation cream or gel composition, or can be put up in asolid gel stick or powder composition. Such compositions can, apart fromthe presence of the silica particles, be of conventional composition.However, as stated above, it is preferred to put the composition up in avolatile fluid carrier medium which evaporates to form the fine passagesor interstices in the silica deposit on the skin.

The composition of the invention is applied to the area of the skinwhich is affected by the acne or similar disorder. The amount of thecomposition applied will depend upon the extent and severity of theacne, but will typically apply from 10 to 500, preferably 20 to 200,milligrams of silica particles per square cm of the skin. If needed, theapplication can be repeated as required to eliminate the acne, forexample at four hourly intervals. In severe cases, the composition maybe applied to a solid carrier, for example a self adhesive plaster,bandage or the like, which is applied to the skin and left in place fora prolonged period. The use of a solid application vehicle to retain thecompositions upon the skin may also be desirable where the compositionscontain highly deliquescent forms of silica and it is desired to preventexcessive acquisition of moisture by the silica from the environment asopposed to absorption of fluid from the skin.

I have found that the composition of the invention is surprisinglyeffective in the treatment of the symptoms of acne and that othermedical treatment may not be required. The silica may therefore be thesole dermatologically active ingredient in the composition. I believethat the removal of fluid from the affected area of the skin alsoreduces the activity of bacteria within the affected areas. However, ifdesired other active ingredients, for example medicaments, eg.anti-biotics, anti-bacterials, retinoids and/or benzoyl peroxide, may beincorporated in the compositions of the invention and/or may be appliedto the affected area in a separate treatment. Furthermore, thecompositions of the invention may also find use in the treatment ofinflamed areas of the skin which are caused by other mechanisms than theactivity of the sebaceous glands, for example inflamed areas around hairfollicles, and the term related disorders is used herein to denotedisorders of the skin which exhibit the same type of symptoms as acneitself.

Following the application of the composition of the invention to theaffected area, fluid from the underlying skin migrates the silicaparticles, at a rate which I believe is greater than that at which theskin can replenish the skin fluids, to form a slightly dampened powderdeposit upon the skin. This can be removed by brushing or by washing theskin, preferably after a period of from 5 to 60 minutes; or can beallowed to remain upon the skin to continue to absorb fluid from theskin, notably where the silica particles are incorporated in a cosmeticcomposition such as a foundation cream or powder. As indicated above, wehave found that the use of a volatile alcohol, ketone or ester as thecarrier for the silica particles aids drying of the composition on theskin and the absorption and/or adsorption of fluid from the skin by thesilica particles.

The compositions of the invention can be made by any suitable method,for example by milling the components together. If desired, thecompositions can be made by mixing some or all of the ingredients in ahigh speed mixer, for example a high shear mixer, to form a stableviscous gel or paste of the solid particles in the fluid carrier medium.However, we have found that problems can arise if excessive shearworking of the composition is carried out. The optimum amount of suchshear working of the composition will depend upon the nature andrelative proportions of the ingredients and can readily be establishedby simple trial and error tests.

The invention thus also provides a method of making a composition of theinvention which comprises mixing the ingredients of the compositiontogether.

The invention will now be illustrated by the following Examples in whichall parts and percentages are by weight unless stated otherwise:

EXAMPLE 1

A composition was prepared by mixing fine aerogel silica particles withjust sufficient surgical spirit to form a viscous paste containingapproximately 50 parts of silica and 50 parts of surgical spirit. Thepaste was applied as a thick coating to the acne spots of a sixteen yearold girl suffering from acne. The alcohol rapidly evaporated from thecoating of paste applied to the skin and formed a powdery residue uponthe skin. After 30 minutes this residue was washed off the skin and theacne spots examined. It was noted that the spots had diminished in sizeand redness to the point where they were not embarrassingly visible. Thetreatment was repeated on a daily basis and it was noted that the acnespots virtually disappeared after three days. It was also noted that thetreatment did not cause excessive drying, cracking or chaffing of theskin which would have been expected if the sole action of the silica wasas a desiccant.

EXAMPLE 2

A white viscous gel was made by shear mixing 10 parts of fine powderedsilica with a particle size of less 5 micrometres with 90 parts ofethanol and the gel was filled into 40 gm capacity aluminium tubes.

The gel was applied to the faces of 20 patients, 11 male and 9 femaleaged between 18 and 35 and suffering facial pimples. The gel was appliedto the pimple itself and the surrounding skin area to applyapproximately 1 to 2 g of the gel to an area of about 1 to 4 square cms.The gel was allowed to dry and left on the skin for a period of 60minutes. The powdery deposit was washed off the skin and the status ofthe pimples re-examined after a further 4-6 and 12-18 hours (visits 2, 2and 3). The pimples were assessed by the investigator in terms oferythema, oedema and size and by the patient for redness and swelling.

The total oedema score for the whole group of patients fell from 28 at 1hour after application of the gel (visit 1), to 25 at visit 2 and 14 atvisit 3. The total erythema score for the whole group fell from 28 atvisit 1 to 24 at visit 2 and 20 at visit 3. The redness score assessedby the patients fell from an average score of 20 at visit 2 to 5 atvisit 3 and 14 patients reported no redness at visit 3. The swellingscores assessed by the patients fell from and average score of 8 atvisit 2 to 5 and 17 patients reported no swelling at visit 3.

The patients reported good acceptance with little stinging or burningsensation caused by the gel and the overall inflammation of the skin atthe pimples was markedly reduced.

Whilst the invention has been described above in terms of the treatmentof acne spots, it may also be applied in other conditions where it isdesired to reduce the secretion of excessive fluid in the skin and inthe treatment of such conditions in mammals other than humans.

What is claimed is:
 1. A substantially non-aqueous dermatologicallyactive composition suitable for topical application to the skin of amammal suffering from acne or related disorders of the skin, saidcomposition consisting essentially of the following ingredients:(a) atleast 5% by weight of a particulate anhydrous silica or a precursorthereof having a primary particle size less than 10 micrometers fortreating acne or related skin disorders, said particulate anhydroussilica or the precursor thereof being the dermatologically activeingredient of said composition; and (b) a substantially non-aqueouscarrier medium for said particulate silica comprising a volatile solventselected from alkanols, alkyl glycols, alkyl ketones and/or alkyl estersin which the alkyl moieties contain from 1 to 4 carbon atoms.
 2. Acomposition as claimed in claim 1, wherein said composition contains upto 50% by dry weight of the silica.
 3. A composition as claimed in claim1, wherein said composition comprises from 7.5 to 25% by weight of thesilica.
 4. A composition as claimed in claim 1, wherein the carriermedium is ethanol.
 5. A composition as claimed in claim 1, wherein saidcomposition is put up as a cosmetic composition.
 6. A composition asclaimed in claim 1, wherein said composition is a viscous gel or paste.7. A composition as claimed in claim 6, wherein said compositioncontains a rheological modifier and/or a suspension or dispersionstabilizer.
 8. A composition according to claim 1, wherein the particlesof the silica have been treated to render them more readily wet by skinfluids.
 9. A method for the alleviation of the symptoms of acne andrelated skin disorders in mammals, which method comprises applying tothe affected area of the skin of the mammal a dermatologically effectiveamount of a substantially non-aqueous composition consisting essentiallyof:a. at least 5% by weight of a particulate anhydrous silica or aprecursor thereof having a primary particle size less than 10micrometers for treating acne and related skin disorders; and b. asubstantially non-aqueous liquid carrier medium for said particulatesilica comprising a volatile solvent selected from one or more alkanols,alkyl glycols, alkyl ketones and/or alkyl esters in which the alkylmoieties contain from 1 to 4 carbon atoms.
 10. A method as claimed inclaim 9, wherein the composition contains up to 50% by dry weight of thesilica.
 11. A method as claimed in claim 9, wherein the carrier mediumevaporates from the composition applied to the skin to form a deposit ofsilica particles upon the skin, which deposit contains fine passages orinterstices which exert a capillary action upon the underlying skin toremove fluid from the skin.
 12. A method as claimed in claim 9, whereinthe step of applying the silica or a precursor thereof comprisesapplying from 10 to 500 milligrams of silica particles per square cm ofskin.
 13. A method as claimed in claim 9, and further comprising thestep of allowing the composition to dry and remain on the skin.